Washington: The move comes two days before the 56-year-old would be sworn in on Wednesday along with President-elect Joe Biden, making history as the first female, first Black and first South Asian American vice president.
Harris, a Democrat, has formally submitted her letter of resignation to California Governor Gavin Newsom, CNN reported, quoting a Harris aide.
Harris won her seat in November 2016 and was sworn in January 2017. At the time, Harris was California’s attorney general.
Newsom has already named Alex Padilla, California’s secretary of state, to fill Harris” seat.
The incoming vice president has spoken to Padilla before he comes into office, according to a person with knowledge of the discussion.
Harris made history throughout her career, becoming the first Black woman in California to serve as a senator.
In her November victory speech, she recognised the hard battle women faced to exercise their civic rights and break into the upper echelon of American politics.
“While I may be the first woman in this office, I will not be the last,” Harris said. “Because every little girl watching tonight sees that this is a country of possibilities.”